Nowadays, in the popular mobile phone and flat panel display apparatus, backlight part is the part having the largest power consumption, and the tendency of lightening and thinning the mobile phone and flat panel display apparatus extremely limits variability in size and capacity of the battery. For solving the problems of limitation to capacity of the battery as well as reduction of power consumption, Content Adaptive Brightness Control (CABC) technology is widely used. CABC technology is a backlight power-saving technology that is mainly used in Liquid crystal Display (LCD) screen.
In particular, CABC technology can adjust, according to an image displayed on the screen, a relation between gray level and screen backlight brightness of the image, and substantially maintain the display effect of the image while effectively reducing the screen backlight brightness. For example, the image is brightened by enhancing the gray level by 30%, and the image is darkened by reducing the backlight brightness of the LCD screen by 30%, thus the brightness presented by the image is substantially maintained the same before and after processing, and the power consumption of backlight is reduced by 30%. Backlight brightness can be controlled according to magnitude of driving voltage. An existing liquid crystal display apparatus using CABC technology is shown in FIG. 1. It mainly includes an image data acquisition part 1, a liquid crystal panel 2, a panel driving unit 3, a backlight module 4 and a Pulse-Width Modulation (PWM) backlight modulation unit 5. The image data acquisition part 1 is used to acquire image data SRGB, the panel driving unit 3 drives the liquid crystal panel 2 according to the image data SRGB and generates a backlight driving signal SPWM corresponding to the image data SRGB. The PWM backlight modulation unit 5 performs pulse width modulation to the backlight driving signal SPWM, to form a driving power supply VL to supply to the backlight module 4.
In the liquid crystal display apparatus having the structure mentioned above, the dimming mode of the backlight is a single mode of performing pulse width modulation to the backlight driving signal SPWM. PWM dimming has high conversion efficiency when the required backlight brightness is large; but the duty ratio of PWM dimming is very low when the required backlight brightness is small, which greatly reduces the efficiency of backlight driving, and goes against the effective use of the entire system energy of the liquid crystal display apparatus.